Lubricants containing metal carboxylate and metal phosphate



MIL

United States LUBRICANTS CONTAINING METAL CARBOXYL- ATE AND METAL PHOSPHATE Arnold J. Morway, Clark, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware This invention relates to lubricating oil compositions. Particularly, it relates to lubricants containing an alkaline earth metal salt of a low molecular weight carboxylic acid and a metal phosphate.

Alkaline earth metal salts of C to C fatty acids are useful in lubricating oil compositions for improving the extreme pressure properties and anti-wear properties of the lubricant. Also certain metal phosphates (e.g. trisodium phosphate) are very valuable materials for addition to lubricating compositions as they also serve as extreme pressure and anti-Wear agents. In addition, many of these phosphates serve to prolong the effectiveness of conventional antioxidants by neutralizing the acidic products which result from oxidation degradation of the oil, thereby preventing these acidic materials from further catalyzing the decomposition of the oil. While both the alkaline earth metal carboxylates and the phosphates are valuable addition agents for oil, they are not dispersible per se in the oil to form stable lubricating oil compositions. In order to effectively use these materials it has been the practice to incorporate other agents to suspend these salts in oil. Thus, various soap and salt thickeners and so-called soap-salt complex thickeners have been used to stably incorporate the low molecular weight carboxylates into oil. In other instances, certain surfactants have been used, or the carboxylate is added in the form of a hydrate. In the case of the phosphates, heretofore it has only been possible to effectively use them in the form of greases. Thus, a sufficient amount of another thickener such as a soap or perhaps a polymeric thickener has been necessary to impart enough body to the oil to make a solid grease and thereby suspend the phosphate.

It has now been found that these low molecular weight carboxylates and the metal phosphates, when used together in oil, tend to suspend each other to thereby form a stable oil dispersion. Thus, stable fluid lubricants can be made containing the low molecular weight carboxylate and the phosphate. Based upon this discovery, very large quantities of these two materials may be incorporated into the oil without undue thickening of the oil or the necessity of forming a stable grease. As another advantage, the need for more expensive higher molecular weight soaps or the necessity for forming mixed soapsalt complexes as well as the attendant expense has been eliminated.

The low molecular weight carboxylates useful in this invention are those alkaline earth metal (e.g. calcium strontium, magnesium or barium) salts of a C to a C fatty acid (e.g. acetic, propionic, butyric acid, etc.). These metal carboxylates are best prepared in situ in the lubricating oil by neutralization of the appropriate acid or acid anhydride with a metal base, e.g. calcium hydroxide. By this in situ formation a very fine degree of dispersion of the carboxylate in the lubricating oil is obtained. Of course, the carboxylate in a powdered form may be directly dispersed in the lubricating oil or atet ICE

2 it may be added to the lubricating oil in a water solution or dispersion and the excess water removed by heating.

The preferred carboxylate is calcium acetate, in either an anhydrous form or in the form of a monohydrate. If the calcium acetate is formed by neutralizing acetic acid with calcium hydroxide at a temperature between about 200 to 300 F. the monohydrate will result. Heating above 300 F. results in anhydrous calcium acetate.

The phosphate materials which may be used in preparing the compositions of the invention include the alkali metal (e.g. sodium and lithium) and the alkaline earth metal (e.g. calcium, barium, magnesium) salts of phosphoric acid, i.e. ortho, meta and pyrophosphoric acid. Preferred salts are those of orthophosphoric acid such as tricalcium orthophosphate, monocalcium dihydrogen orthophosphate, trisodium orthophosphate and disodium hydrogen orthophosphate.-

The lubricating oil used in the compositions of the invention may be a mineral lubricating oil, a synthetic lubricating oil, or mixtures thereof. Synthetic lubricating oils which may be used include esters of dicarboxylic acids (e.g. di-2-ethylhexyl sebacate); esters of glycols (e.g. C Oxo acid diester of tetraethylene glycol); complex esters (e.g. the complex ester formed by reacting one mole of sebacic acid With two moles of tetraethylene glycol and two moles of 2-ethyl-hexanoic acid); formals, silicones, carbonates, polyglycols and other synthetic lubricating oils known in the art.

Particularly desirable synthetic oils are those diester oils containing a total of 15 to 40, e.g. 20 to carbon atoms and consisting of saturated hydrocarbon chains linked by two ester linkages. Such esters are prepared from C to C alkanols reacted with C to C alkanedioic acids; or C to C glycols reacted with C to C alkanoic acids. Preferred esters are those prepared from alkanedioic acids and Oxo alcohols. The Oxo alcohols are isomeric mixtures of branched chain primary alkanols produced by the reaction of an olefin with hydrogen and carbon monoxide in the presence of a cobalt catalyst to form a mixture of aldehydes, which aldehydes are then hydrogenated to form the OX0 alcohol. Such Oxo alcohols and their preparation are well known in the art. Specific examples of diesters of the above types will include: di-(C Oxo) adipate; di(2-ethylhexyl) sebacate; di-(C Oxo) sebacate; 1,6-hexamethylene glycol di -(2- ethylhexanoate) and 1,10 -decamethylene glycol di- (caprylate) The compositions of the invention will contain a major amount of lubricating oil and about 1.0 to 50.0 e.g. 3.0 to 45.0 wt. percent of the carboxylate-phosphate combined additive. This additive combination in turn will generally comprise about 1.0 to 3.0, preferably 1.0 to 2.5 molar proportions of the carboxylate per molar propor tion of the phosphate. In terms of weight proportions, this will roughly correspond to about 1.3 parts by Weight of carboxylate per about one part by weight of phosphate.

The oil composition may also contain other additives. Examples of such additives include viscosity index improvers such as polyisobutylene; corrosion inhibitors such as sorbitan monooleate; pour depressants; dyes;detergents and the like.

As indicated above the phosphate and carboxylate stably suspend each other in oil so that no salt precipitation occurs. However, in certain instances if the oilsalt system is completely anhydrous, a small amount of the oil Will tend to separate from the main mass upon prolonged storage. This is not a serious problem since upon mixing a homogeneous mass is readily obtained. However, it does represent a slight marketing deterent. It has been further found that this can be inhibited by Patented Dec. 13, 1960 various surface active agents. One such type of surface active agents are copolymers of ethylene glycol and propylene glycol which are commercially available under the trade-name of- Pluronics. These materials havev where a and c are integers of value 2 to 150, and b is an integer of to 170. The molecular weight may vary considerably but generally is between 1,000 and 20,000, e.g. 1,000 to 10,000. Thus, Pluronic L-44, Pluronic L-62, and Pluronic F-68 appear to have molecular weights of about 2800, 230.0 and 8700 respectively; The ratio of the ethylene oxide groups to the propylene oxide groups in the Pluronic materials vary between about 3/1 to 1/3. Thus, in Pluronics L 62,analysis showed a ratio of about 1.15 moles of ethylene oxide per mole of propylene oxide. However, the ratio of these two alkylene oxide groups is not critical for the present invention since operable materials will include ethylene or propylene polyglycols per se.

Another useful surface active agent includes N,N- polyalkyleneoxy disubstituted alkyl amine such as Ethomeen T/25 which has the formula:

where R is an alkyl group derived from tallow and the total number of ethylene oxide groups is about 15. Still another surface active agent which can be used is Duomeen T dioleate which has the structure:

wherein the alkyl group is derived from tallow. Other surface active agents which may be used are described in my copending patent application Ser. No. 692,041, filed on October 24, 1957. Generally, about 0.05 to about 2.0 wt. percent based on the weight of total composition of surface active agent will be sufficient to prevent oil separation or bleeding under even the worst adverse conditions.

The carboxylate-phosphate materials of the invention may also be incorporated into greases thickened with any conventional grease thickeners such as: soaps,.soapsalt or mixed-salt complexes, polymeric thickeners (e.g., polymers of C to C monoolefins of 10,000 to 200,000 mol. wt. such as polyethylene), or inorganic thickeners (e.g., clay, carbon black, silica gel, etc.). The carboxylate and phosphate materials may be directly dispersed in said greases; ora lubricating oil dispersion of the carboxylate-phosphate materials may be added to the other greases; or other thickeners may be added or formed in the lubricating oil dispersion of the carboxylate and phosphate, etc. By using the carboxylate-phosphate combination of the invention with other grease making materials, not only does the combination impart extreme pressure, anti-wear and antioxidant properties to the composition, but the amount of other, grease thickeners required to produce a grease of a given hardness is substantially reduced.

The invention will be furtherunderstood by the following examples.

EXAMPLE I A grease composition wherein all parts are by weight was prepared as follows:

17 parts of hydrated lime was mixed with 47 parts of a mineral lubricating oil having a viscosity of 80 SUS at 210 F. to form an intimate mixture. 25 parts of glacial acetic acid was then slowly added while stirring, the heat of reaction causing the temperature of the mixture to.rise to a maximum of about 210 F. After all the acetic acid was added, the mixture was then stirred for another /2 hr. Then, 10 parts of trisodium orthophosphate was stirred into the mixture, after which 1" part of phenyl a-naphthylamine was added. No external heating was applied. A solid grease material resulted, which was homogenized by passage through a Morehouse mill having a .003" opening.

EXAMPLES II AND III-A The compositions of these examples were prepared by mixing additional amounts of mineral lubricating oil-withthe product of Example 1.

EXAMPLE III-B A sample of the product of III-A was heated to 320 F. in order to completely dehydrate the product and form anhydrous calcium acetate. The composition was then homogenized in a Gaulin homogenizer operating at 5000 p.s.i.

EXAMPLE IV EXAMPLE V The product of Example IV was cut back with additional mineral lubricating oil after which the blended product was passed through a Gaulin homogenizer operating at 5,000 psi.

EXAMPLE VI A portion of the product of Example V was heated to a maximum temperature of 325 F. in order to dehydrate the composition and form anhydrous calcium acetate.

The compositions and properties of the products prepared above are summarized in Table I.

As seen from Table I, solid grease compositions may be prepared which contain only the calcium acetate and sodium phosphate as shown by Example I. The product of Example I was tested in the Anti-friction Bearing Manufacturers-National Lubricating Grease Institutes test machine and had a lubricating life in excess of 1800 hours. The grease composition of ExampleI can be readily cutback with varying amounts of lubricating oil to form either a softer grease as shown by Example II, or to form fluid products as illustrated by Examples III-A and III-B. Examples II, III-A and III-B further show that the resultingproduct had good wear characteristics as indicated by the 4-ball wear test and good load-carrying ability as indicated by the Almen test. Furthermore, such products were stable even when maintained at a high temperature for an extended length of time. Thus, in Examples III-A and III-B, there was no separation or settling of the solids after being maintained in an oven for 8 days at 350 F. Example IIIB did show a slight separation of oil from the body of the material. However, this is not a serious disadvantage since upon stirring the original composition would be obtained. Also, no discoloration of the oil occurred during these oven tests, thus indicating that there was no serious oxidation degradation of the mineral oil. Examples IV, V and VI illustrate compositions further containing a minor amount of a polyglycol .type surface active agent. Example VI did not show the slight oil separation that had occurred in Example III-B during the oven test. This improvement was due to the presence of the small amount of Pluronics L-62.

The above data-further illustrates that the calcium acetate maybe present either in a hydrous form, i.e. as a. monohydrate as illustrated by Examples II and III-A or it may be present in the anhydrous .form as illustrated by Example III-B.

Table 1 Examples Components (Weight Percent) I II III-A III-B IV V I Glacial Acetic Acid. 25.0- 12.5 5.0. 5.0 25.0 5.0 5.0. Hydrated Lime 17.0 8.5 3.4 3.4 17.0 3.4- 3-4. Sodium Phosphate (Na PO 10.0. 5.0.. 2.0-- 2.0.. 10.0- 2.0-- -0. Phenyi -n phthylamine 1 0.5 0.2. 0.2. 1.0- 0.2-- 0.2. Pluronics L-62 2.0 0.4.- 0.4. M neral lubricating oil so sUs at 210 F) 89.4-. 45.0.- 89.0- 8 -0. Mineral lubricating oil (55 SUS at 210 F Form of Calcium Acetate anhydrous. monoonoanhydroushydrate. hydrate.

Properties:

Appearance Droppmg Point, F

Penetration 77 F. mm./10:

Worked 60 strokes 20 Worked 10.000 strokes Viscosity at 100 F. (SUS)- 1,925-- 1,575 semi-flu d." -fl Viscosity at 210 F. sUs) 13s 1 0 4-Ball Wear Test (1800 r.p.m.- Kg. 0.31.- 0.29-- 0.28--. 0.41.. 0.

Load75 O.1 hour). Almen Test (Wgts. carried):

Shock Loadin 13 Gradual Loadin 15 15 15 Stability 8 days at 350 F.)

1 Smooth, uniform product. 2 Excellent, no salt separation. 3 Excellent, no salt or oil separation.

EXAMPLE VII 0.8 part by weight of polyethylene of 250,000 molecular weight was dispersed in 88.2 parts by weight of a mineral lubricating oil having a viscosity of 80 SUS at 210 F. by stirring the mixture while heating to 330 45 F. The oil-polyethylene dispersion was then cooled to 100 F. and 0.4 part by weight of Pluronics L-62 was added along with 3.4 parts by weight of hydrated lime. After blending in these last two named components into the composition, 5.0 parts by weight of glacial acetic acid was then slowly added during which the temperature rose to a maximum of about 210 F. The composition was then stirred for an additional /2 hour after which 2 parts by Weight of trisodium orthophosphate was added, followed by an additional 30 minutes stirring. The resulting composition was then homogenized by passage through a Morehouse mill having a .003" clearance.

EXAMPLE VIII-A Mineral oil, Ethomeen T/25 (previously described) and hydrated lime were intimately mixed without external heating. Glacial acetic acid was slowly added while stirring and the temperature of the mixture rose to 210 F. Mixing for another half-hour was continued and disodium acid orthophosphate was added and stirred' in, followed by the addition of phenyl a-naphthylarnine. A solid grease resulted which was passed through a Morehouse mill having a 0.003" opening.

EXAMPLE VIII-B The product of Example VIII-A was cutback with additional mineral oil and homogenized at 4,000 p.s.i.

Table 11 Examples Components (Weight Percent) VII VIII-A VIILB VIII-C Hydrated Lime 3.4 14.0 7.0 2.8. Glacial Acetic Acid 5.0.- 20.0-.. 10.0.-. 4.0. Trisodiurn Phosphate (Na PO4) 2.0 Disodium Acid Phosphate 20.0.-. 10.0 Pluronics L-G2 0.4.-- Ethomeen T/25 2.0.. 1.0. 0.4. Polyethylene (250,000 now.) 0.8.. Phenyl alpha-Naphthylamine 0.2.- 1.0.- Mineral Lubricating Oil (80 SUS at 210 F.) 88.2 43.0 Mineral Lubricating Oil SUS at 210 F.) Properties:

Appearance Smooth fluid Solid grease. Solid grease.

Penetration 77 F. mm./10 (ASTM):

Unworked. 21 29% Worked Strokes 220 310 Worked 10,000 strokes" 325 Dropping Point, F 600+ Consistency:

Via/100 F- ..SUS 2,500 1,945. Vis./210 F 2,000-- 5. 4 Ball Wear Test (1800 0.29..- 0.32.

C.-l hour). Almen Test (Wgts. carried):

Gradual Loadin 15 15 15. Shock Loading 11 15 10. Pin Condition Excellent- Oven Test:

8 Days at 210 F..- ()i Lubrication Life-Hours(250 F.-10,000 r.p.m.) 1,710 hours.

l N 0 separation or discoloration.

phate and disodium acid orthophosphate to form both solid-greases and fluid lubricants,- dependingupon the relative amounts of salt material used.

EXAMPLE IX In this'composition 30 parts by-weight of mineral lubricating oil having a viscosity of 80 SUS at 210 F., 20 parts by weightofa 'di-(G -Oxo) 'adipateand-24-parts by weight of hydrated lime were intimately mixed to form a smooth-dispersion.- The C 'Oxo'alcoliolusedin preparing the ester was obtained bylsiibje'c'ting tripropylene to the previously described Oxo process. Then a mixture consisting of parts by weight of glacial acetic acid and 10 parts by weight of an 85 wtrpercent concentrate of orthophosphoric acid was added to the main mixture while stirring andwithout externalheating. As the acid mixture was added, the heat of reaction caused the composition to reach a' maximum temperature of 220 F. The composition was thenexternally heated to attain a temperature of 320 F. in order to dehydrate the product. It was noted that as long as waterwas present the mixture appeared as a smooth:grease like'rnaterial. However, as the water was removed by continued heating the product became more fluid and grainy. The resulting hot anhydrous fluid dispersion was then cooled to 200 R, where 1 part by Weight of phenyl a-naphthylamine was added, following which'the mixture was cooled to 150 F. At'this point the product was passed'through a Morehouse mill. An excellent fluid product having a very slight degree of graininess resulted.

EXAMPLE X The product of Example IX was cutback with additional di-(C Oxo) adipate, then passed through a Gaulin homogenizer operating at 3,000 p.s.i.

EXAMPLE XI A grease was prepared in the general manner of EX- ample I. However, a different proportion of materials was used, tricalcium orthophosphate was used in place of the trisodium orthophosphate and a small amount of Pluronics L-62 was added before the addition of the acetic acid.

EXAMPLE XII A portion of the product of Example'XI was mixed with additional mineral oil and the resulting mixture was heated to 440 F. while stirring. The mixture was then cooled to 120 F. and milled ina Morehous'e'" mill at a 0.003" opening and then filtered. Nothing filtered out.

EXAMPLE XIII Afterall the acid mixture was added, the mixture was a stirred for another half hour. Then externalheating was initiated andthe temperature raised to 320 F. At this point, heating was discontinued and the dispersion was rapidly cooled to 150 F. by passing cold water through the kettle jacket, and phenyl a-naphthylamine was added. The resulting grease was Gaulin homogenized at 6,000 p.s.1.

EXAMPLE XIV A portion of the product of Example XIII was cutback with additional lubricating oil.

The properties and composition of the preceding lubricants in terms of their original ingredients are summarized in Table III.

Examples IX, X, XIII and XIV demonstrate the direct use of orthophosphoric acid to form an orthophosphate in situ. calcium orthophosphate. Also, the above examples illustrate the formation of both fluid and grease compositions as well as demonstrating the use of a diester oil and various additive materials.

While the preceding working examples have been dirooted to the use of orthophosphates, the meta and pyrophosphates may also be used. In fact, depending upon the temperatures involved and whether or not water is present, the form of the phosphate may change. Thus, sodium diacid orthophosphate, upon heating, will be converted into the metaphosphate of sodium by losing water. However, the reaction is reversible as upon the addition of water, the orthophosphate is again formed.

The above is to illustrate the fact that even during use, the composition of the lubricant might change. However,

Table III Components (Weight Percent) Examples XIV Glacial Acetic Acid Hydrated Lime...

Tricalcium Phosphatei OrthoPhosphorlc Acid (85%).. 7

Duomeen 'I Dioleate Pheny a-naphthylamina- Dl-(Cm'Oxo A'dipate) Mi npral Lubricating Oil (80 SUS at 210 Properties:

Appearance Penetration 77 F. mm./10 (ASTM):

Unwor Smooth fluid Smooth fluid Smooth grease.

, Worked strokes. Dropping Point, F Consistency:

Via/100 F. (SUS) Vis./2l0 F. (SUS) 4-Ball Wear Test (1,800 r.p;m.10 Kg.

Load- O.1 hour) Scar dia. mm. Almen Test (Wgts. carried):

Gradual Loading. 1

. 15. I is Shock Loadin 1 a Pin Condition Excellent-..

Oven Test:

14 day's'at 210 F I No separation or discoloration.

Slight scratch.

Examples XI and XII illustrate the use' of tri-' any of the forms noted above are considered as within the scope of this invention.

In summary, this invention is based upon the discovery that certain metal salts of low molecular weight fatty acids and metal salts of phosphoric acid tend to suspend each other in oil when used in certain critical ratios. Thus, either greases or fluids may be prepared in which these two salts are the sole salt components of the oil, e.g. the need for salts of higher molecular weight fatty acids as suspending or thickening agents, such as calcium stearate can be avoided.

What is claimed is:

1. A lubricating composition comprising a major proportion of a lubricating oil, an alkaline earth metal salt of a C to C fatty acid and a metal phosphate, wherein the metal component of said phosphate is selected from the group consisting of alkali metals and alkaline earth metals, wherein there is about 1 to 3 parts by weight of said fatty acid salt per 1 part by weight of phosphate, wherein the amount of said fatty acid salt and said phosphate is about 1 to 50.0 wt. percent of the total composition and wherein said metal salt of said C to C fatty acid is the sole fatty acid salt present in said composition.

2. A lubricating composition according to claim 1, wherein said phosphate is selected from the group consisting of ortho, meta and pyrophosphates.

3. A lubricating composition according to claim 1, wherein said lubricating oil is selected from the group consisting of mineral lubricating oils and synthetic diester lubricating oils.

4. A lubricating composition according to claim 1, which also includes about 0.05 to 2.0 wt. percent, based on the total weight of the composition, of a material selected from the group consisting of: copolymers of ethylene glycol and propylene glycol having the formula:

2 4 )a.( 3 6 )b( 2 4 )c where a and c are integers of value 2 to 150, and b is an 10 integer of 5 to N, N polyalkyleneoxy disubstituted alkyl amines having the formula:

)CHaCH-zOhH R-N (CHzCH20)xH where R is an alkyl group derived from tallow and the total of both xs is about 15 and material of the formula:

wherein the alkyl group is derived from tallow.

5. A lubricating oil composition according to claim 1, wherein said metal salt of said fatty acid is calcium acetate and said metal phosphate is an orthophosphate.

6. A lubricating composition according to claim 5, wherein said metal phosphate is selected from the group consisting of tricalcium orthophosphate, trisodium orthophosphate, and disodium acid phosphate.

7. A lubricating composition according to claim 5, wherein said calcium acetate is anhydrous.

8. A lubricating composition according to claim 5, wherein said calcium acetate is calcium acetate monohy drate.

9. A method of lubricating relatively moving contacting surfaces which comprises maintaining between said surfaces the composition of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 2,079,051 Sullivan May 4, 1937 2,384,551 Jehle Sept. 11, 1945 2,513,680 Schott et a1. July 4, 1950 2,607,735 Sproule Aug. 19, 1952 2,671,758 Vinograd Mar. 9, 1954 2,744,870 Stillbroer et a1. May 8, 1956 2,863,847 Morway Dec. 9, 1958 Patent No, 2964 475 December 13 1960 Arnold Jo Morway It is hereby certified that err ent requiring correction and that th corrected below.

or appears in the above numbered pate said Letters Patent should read as Column 2, line 57 for, "1,3" read l to 3 Signed and sealed this 30th day of May 1961.

SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. A LUBRICATING COMPOSTION COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL, AN ALKALINE EARTH METAL SALT OF A C2 TO C5 FATTY ACID AND A METAL PHOSPHATE, WHEREIN THE METAL COMPONENT OF SAID PHOSPHATE IS SELECTED FROM THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS,WHEREIN THERE IS ABOUT 1 TO 3 PARTS BY WEIGHT OF SAID FATTY ACID SALT PER 1 PART BY WEIGHT OF PHOSPHATE WHEREIN THE AMOUNT OF SAID FATTY ACID SALT AND SAID PHOSPHATE IS ABOUT 1 TO 50.0 WT. PERCENT OF THE TOTAL COMPOSITION AND WHEREIN SAID METAL SALT OF SAID C2 TO C5 FATTY ACID IS THE SOLE FATTY ACID SALT PRESENT IN SAID COMPOSITION. 